First off, when you did the front suspension, did you check that both front springs are the same length when off the car?
If so, then you have the same problem as Lucky did. Not surprising as they are both similar ages. If you take the trouble to measure the rear spring pocket heights in the base unit, I bet you'll find that one is a lot higher than the other. Having spent a lot of time doing the measurements on mine, I think I can shortcut all that for you and simply say, remove all packing bar the rubber washer on the high side, and then pack the low side until both are level. You may be surprised at just how much packing this needs!I presume that you spotted the packing rings that live in the spring pockets of the trailing arms?
Chris